Senior GNC Engineer (Navigation)

About the role

Why Castelion, Why Now

Castelion is moving incredibly fast to develop and deliver advanced defense systems at a time when execution matters more than ever. We believe focus and technical excellence are decisive advantages - and we are building a team that can deliver real capability, not just concepts.

This is a rare opportunity to join at an early stage, where your work will directly shape critical systems, influence major technical decisions, and have immediate, real-world impact.

Senior GNC Engineer (Navigation)

We are seeking a Senior GNC Engineer to develop advanced navigation solutions for Castelion's long-range hypersonic strike vehicles. This role is critical to enabling precise state estimation across all mission phases, including GPS-denied environments. You will work hands-on with multidisciplinary engineering teams to design, analyze, implement, and validate multi-sensor navigation algorithms, including star tracker-based alternative navigation and sensor fusion architectures, in a fast-paced, hardware-driven environment.

Responsibilities

Design and develop navigation algorithms for high-speed flight vehicles, including inertial navigation and alternative navigation (alt-nav) methods
Develop and implement multi-sensor fusion architectures using Extended Kalman Filters (EKF) and related estimation techniques
Integrate data from IMUs, star trackers, GNSS (when available), and other onboard sensors to provide robust, high-accuracy state estimation
Work closely with avionics, flight sciences, and flight software teams to integrate navigation algorithms into real-time embedded systems
Conduct modeling, simulation, and analysis to evaluate navigation performance, error growth, and robustness under GPS-denied and degraded conditions
Support hardware-in-the-loop (HIL) testing, flight testing, and post-flight analysis, translating results into system-level improvements
Characterize sensor performance, biases, and error sources to inform filter design and tuning
Develop tools and frameworks for navigation algorithm development, verification, and validation
Mentor junior engineers and contribute to best practices in navigation and estimation
Partner closely with program leadership to make technical trades aligned with mission success

Basic Qualifications

Bachelor's, Master's, or PhD in Aerospace Engineering, Electrical Engineering, or related field
5+ years of experience in navigation algorithm development, analysis, and validation for aerospace or high-performance dynamic systems
Strong background in estimation theory, including Extended Kalman Filters (EKF) and multi-sensor fusion
Experience with inertial navigation systems (INS) and integration with external aiding sources (e.g., GNSS, star trackers, or similar sensors)
Familiarity with alternative navigation (alt-nav) techniques for GPS-denied environments
Proficiency in modeling and simulation tools such as MATLAB/Simulink or equivalent
Experience with 3DOF and 6DOF simulation environments and real-time implementation of navigation algorithms
Strong understanding of sensor error modeling (IMUs, star trackers, etc.) and calibration techniques
Familiarity with flight software integration and real-time embedded systems
Strong problem-solving mindset, thriving in a fast-paced, hardware-rich, high flight cadence environment

Other Duties

Please note this job description is not designed to cover or contain a comprehensive listing of activities, duties or responsibilities that are required of the employee for this job. Duties, responsibilities and activities may change at any time with or without notice.

Benefits And Perks

All full-time employees are granted meaningful long-term equity, sharing in the company's significant growth trajectory. We offer four (4) weeks of paid time off, ten (10) company-paid holidays, and comprehensive health benefits - including 100% employee-covered medical and strong dependent coverage, along with dental and vision plans. We also provide paid parental leave to support growing families, a $100 monthly fitness stipend to promote health and performance, and onsite EV charging for convenience. In addition, employees enjoy perks like catered meals, company-covered food during high-demand periods, and a fully stocked kitchen to stay fueled throughout the day.

While this position does not currently require a U.S government-issued security clearance, it may in the near future. Therefore, the ability to obtain and maintain a U.S. government–issued security clearance is required. U.S. citizenship is required, as only U.S. citizens are eligible for a security clearance.

Affirmative Action/EEO Statement

Employment with Castelion is governed on the basis of competence and qualifications and will not be influenced in any manner by race, color, religion, gender, national origin/ethnicity, veteran status, disability status, age, sexual orientation, gender identity, marital status, mental or physical disability or any other legally protected status.